High Intensity Focused Ultrasound (HIFU) offers a non-invasive, non- surgical, bloodless, outpatient treatment option for uterine fibroid tumors. These tumors develop in over half of all women, and account for approximately 30% of all hysterectomies. This proposal will develop an array-based transvaginal HIFU probe with electronic beam control as an optimal method of fibroid treatment. The proximal transvaginal position facilitates optimal penetration control, improved focusing and minimized risk of complication. Phase I focuses on researching aspects of HIFU not yet understood. A combined HIFU array with an imaging array in the center is envisioned, however it could exhibit adverse side lobe energy distributions due to non-linear effects. This issue will be researched with the development of new high intensity hydrophone/thermocouple combination needle probes. Properties will be evaluated in a water tank, gel phantom and animal uterus. The effect of tissue orientation will be investigated and the heating pattern will be visualized with a new clear gel that opacities with heat. In Phase II the arrays will be integrated into an ergonomic probe in preparation for clinical studies in Phase III. Dramatic improvements in patient treatment, reduction in health care costs, reduced recovery time and preservation of women's fertility are the potential results. PROPOSED COMMERCIAL APPLICATION: The goal of this research is to develop a non-surgical, outpatient treatment system for uterine fibroid tumors based upon high intensity focused ultrasound (HIFU). It is anticipated that this treatment will improve patient care, facilitate an alternative to hysterectomy, and result in significantly lower treatment cost. Ultimately, this treatment approach may also provide an option to preserve fertility and improve reproductive outcomes in patients with fibroid tumors.